Decomposition of complex metal phosphate salts



Patented June 3, 1 952 DECOMPOSITION OF COMPLEX METAL PHOSPHATE SALTS Dieter M. Gruen and Joseph J. Katz, Chicago, Ill., assignors to the United States of America as represented by the United States Atomic En-.

ergy Commission No Drawing. Application June 19, 1951, Serial No. 232,466

9 Claims. 1

The process of the present invention is concerned with a method of decomposing complex metal phosphate salts and recovering the metal values substantially free of phosphorus. The process is particularly concerned with the recovery of the titanium subgroup metals from complexes of said metals with phosphorus oxychloride and phosphorus pentachloride.

The term titanium subgroup metals or IV-B subgroup metals as used in this specification and claims refers to the three elements of the IV-B subgroup of the periodic table, namely, titanium, zirconium and hafnium.

Zirconium is a metallic element having many hnghly desirable characteristics. It has a very high melting point, a specific gravity approximately 20% less than plain carbon steel, and excellent corrosion characteristics. Moreover, it is comparatively abundant. It is, however, rather difiicult to recover pure zirconium from zirconium ores. One of the chief difficulties encountered in such recovery is the problem of separating zirconium from the hafnium with which nearly all natural zirconium is associated. One method of separating zirconium from hafnium is a volatility type of process in which the phosphorus oxychloride or phosphorus pentachloride complexes of zirconium and hafnium are separated by fractional distillation. One disadvantage of this process, however, is the difficulty of recovering the zirconium or the hafnium from the resultant enriched metal complex distillate or residue in a state sufiiciently free of phosphorus that it may be readily converted to a phosphorus-free metallic state.

It is an object of the present invention to provide a method for recovering the titanium subgroup metal values from phosphorus chloride and phosphorus oxychloride complex salts of said metals.

It is an additional object of the present invention to provide a method of recovering zirconium in a substantially phosphorus-free state from complexes containing zirconium, chlorine, phosphorus and oxygen.

It is an additional object of the present invention to provide a method of decomposing complex salts of hafnium, phosphorus and chlorine and the recovery of hafnium values substantially free of phosphorus.

Other objects will be apparent from the following detailed description.

The process of recovery of the group IV-B metals from phosphorus chloride and phosphorus oxychloride complexes of these metals depends.

2 primarily upon the decomposition of these complex salts by reaction of the salts with a monohydric alcohol. The process of the present invention comprises broadly reacting a group IV-B metal phosphorus oxychloride complex salt with a monohydric alcohol having less than five carbon atoms, then dissolving the reaction mixture in water, and recovering the group IV-B metal from the solution by precipitating the metal as the hydroxide. The metal values are thus recovered in a form substantially free of phosphorus.

While we do not wish to be bound by any theory advanced, it is believed that the present process operates upon the principle of using the IV-B metal phosphorus chloride or oxychloride complex as a phosphorylating agent for the formation of an organic phosphate with the monohydric alcohol. This organic phosphate binds the phosphorus so strongly as to prevent precipitation of the phosphorus during the subsequent dissolution of the metal salt in water and its precipitation and recovery as the metal hydroxide. In any event, it is essentiol that the step of reacting the alcohol with the complex salt and the steps of dissolution of the alcohol-complex salt mixture in water be carried out in that order.

The process of the present invention is appli-' cable to the recovery of titanium, zirconium or hafnium from complexes of these metals with phosphorus'oxychloride or phosphorus penta The process which is essentially the chloride. same for the recovery of all three metals is illustrated by the following description of the recovery of zirconium.

The zirconium-phosphorus oxychloride complex is a dark green substance having a melting point of approximately C. and a boiling point of approximately 360 C. The molecular formula is 3ZrCl4-2POCl3. The pentachloride complex which is believed to have the formula has somewhat higher melting and boiling points the most satisfactory reaction. This involves maintaining the oxychloride complex at a fairly high temperature until contact with the alcohol is made since the complex has a melting point greater th n 109i. .9. as vieus .ie ct qn e- The alcohols a nd particularly thelower alcohols, however, are very volatile. Considerable care must therefore be exercised to prevent the ex: cessive volatilization of the alcohol during mixing with the complex salt. One method-oi prevent ing excessive volatilization is to cool the alcohol before and during mixing so that the temperature of the mixture will be maintained bel w th oiling point of the alcohol. The hoteoinplex s 1 M 7 also be added sufliciently slowly that th'e'bo'iling point of the alcohol is not exceeded in spite of the cooling of the alcohol. Since the higher al cohols have higher boiling points, less rigid trol is required when the propyl and bu tyl alcohols are used. In general, however, methyl and th alcoh l themqst s ti ac r y lds.- ii' a btntxbf new r u it it. an pu an ittpfipi, th'iiibc'ess can be calculated mm the following equation: 1:5ZrGli-1POClfiA-3CI-IaQI-Ij 1'.5Z1C14+3HC1+-(CH3) 31 04 are than swiciiiometri'c amounts or the 1-, nqwva-; are usually used in order to insure complete reaction. I i

admitting the edrhplu'q'n or the reaction betweenthe alcohol and the complex salt, the

mixture is dissolvedinwater and the zirconium 5 ent le 35 in? h d d T hifii'OXY 'usuany furnished by the introduction or hydroxide into tjhe water either berifig or aitfei the ste of dissolving the I v fie saitmixture inure water. A; monium hydrox de a preferable reagent "since at; mama par d by fiep i m e will be rempvedji'om the precipitate subsequent heat j 1 7 11m; or 'potassium hydroxideis theckfireaonhg .z if h e. w ll be firmed d ti'on'al steps will be reduire'd to remove um orpotassium It is desirable to tan-y i h te h m a d atelik after he dis; solution of the alQoli'oF-salt mixture in thewater used since hydrolysis of thealk'yl phosphate may sour on standing. This may result in some phosb riorus o t n oi of t QZi tQfi m h r i whe it w e'que p p ita j d he emov the solution. sto ichioni'etflc or greater duantiti s or th": hydroxide be usedto preatr t' e zir I 'in accordance with the r01- lowing molecular formal-1a:

ZICL; 4NH4OH- Z1' (OH) 4+ 4N'HiC1 Now-that thenprocess of the present invention has enfb feadli es5 sd t sa l er illustrated by reference to the following examples.

Example-I Ten grams of moltenBZrChrZPOCls were added to a flask containing'2'5'ml. of absolute ethyl alcohol; Th'e :flask was cooled and the .-co rnplex was added sufii-ciently slowly so that the tempera ture of "thereaction mixture didnot rise "above '70? C. 'A vigorous reaction ensued resulting in turbid liquid .-phase.. Twenty-five ml. of water were then added to the flask, A 1'5v-ml. quantity QYGNNHAOH was addedto the flask and theres'iiltafit floccul'ent precipitate of zirconium/hydiioxide'was then removed from the-mixture .by centrifugation'. This s'precip'itate was "dissolved-in nitric acid and tested 'forphcsphate with mm monium molybdate reagent. The test was negative indicating that if any phosphorus was present, it was present in a concentration below th sensitivity of this test.

Example II Seven and one' half litei's of n-pi ropyl alcohol was cooled to 5 C. and 1518 g. of molten 3Z1'C14-2POC13 was added directly to the alcohol over-a 'p'jeri'odoi two minutes with constant stirring. The temperature of the mixture rose to C. during this time. The solution was then cooled t'o20 C. and an additional 1055 g. of moltencoinplex I added over a five-minute period, during which time the temperature of the mixture rose to C. The alcohol solution was then diluted with 26.5 liters of hot water and ammonium hydroxide in quantity sufficient to give a permanent orange color with methyl red in the mixture was added to the water. This resulted in a precipitat of zirconium hydroxide which was filtered from the solution and then washed;

Example *III a portion of 13.2 of olten szrfoil-ziocls was slowly-transferredto a cooled fiask containing 12 liters i anhydrous met yl alcohol sumciently slowly that violent reacti was e a/sates; th time required for the atlditio n was about fifteengminutes The mixture was then transa fer-red to'a barrel containing 75 1iter's o f i d wate'rat a temperature of (ififlglxygith constant agitation. Seven and one-half liters of aha ammonia was thenadded to the container. The contents were then checked with-methyl red n dicator which turned yellow indicating a slight excess of ammonia. The precipitateformed allowed 'to settle and the supernatantdecanted. The precipitate wasthen washed three times with distilled waterand finally separated by filtration;

The steps of the rocess, When applied to the dissolution of a group IV-l3 phosphorus penta chloride complexand recovery of the group IV- -B. metal in a phosphorus-free state are the same as those set forth above forthe dissolution of a phosphorus oxychloride complex.

The above detailed description is given tor put poses of illustration and specific details thereof are notintende'd tolimit the scope of .thein ve ntion whichis to be limited only by the following claims;

l, The method of recovering titanium subgroup metal values'from aphosphorus oxychloride com:- plex of said metal, which comprises reacting said complex with a monohydric alcohol-containing les's'than five carbon atoms, dissolving said reaction mass in water, introducing a source of hydr'oxyl ions into said solution whereby said titanium subgroup metal is precipitated as the hydroxide, and recovering saidprecipitate.

2. Theprocess of claim -1 wherein thetitanium subgroup metal is titammn.

-3. The process of claim -1 wherein the'titan-ium subgroup metal is zirconium;

p ss of claim 1 wherein the titaaiam complex salt 3ZrCl4-2P0Cla, which comprises reacting said salt with a monohydric alcohol having less than five carbon atoms, dissolving said reaction mixture in an aqueous hydroxyl containing solution, and recovering the zirconium hydroxide precipitate thus formed.

9. The process of recovering zirconium values from a zirconium-phosphorus oxychloride complex salt, which comprises reacting said salt in the molten state with anhydrous methyl alcohol r 6 while maintaining the reaction temperature below the boiling point of said alcohol, dissolving said reaction mixture in water and contacting V the resultant solution with aqua ammonia whereby zirconium hydroxid is precipitated, and recovering said precipitate.

DIETER M. GRUEN. JOSEPH J. KATZ.

No references cited. 

1. THE METHOD OF RECOVERING TITANIUM SUBGROUP METAL VALUES FROM A PHOSPHORUS OXYCHLORIDE COMPLEX OF SAID METAL, WHICH COMPRISES RACTING SAID COMPLEX WITH A MONOHYDRIC ALCOHOL CONTAINING LESS THAN FIVE CARBON ATOMS, DISSOLVING SAID REACTION MASS IN WATER, INTRODUCING A SOURCE OF HYDROXYL IONS INTO SAID SOLUTION WHEREBY SAID TITANIUM SUBGROUP METAL IS PRECIPITATED AS THE HYDROXIDE, AND RECOVERING SAID PRECIPITATE. 